2 answers

This will provide a guide to individual NPC ship types. It's useful to get things like sec status gain (gain is based on highest sec gain rat killed per arbitrary time period per system, arbitrary period being 10-20 minutes or so).

Reading these makes the selection of the ship to use easier. Can also gives you information on whether you can get away with lightening your tank for more gank (I.e.: removing 2nd repper for a magnetic field stabilizer, remove cap flux coil/shield power relay for a BCU)

Notes

Speed was the focus of my recommendations. Doesn't mean other ship classes can't be used. A kestrel can do almost all L1s with ease for example. Just won't be as fast as a destroyer at mowing down frigs. While I recommend a BC for both L2 and L3s, the fit would be different. In L2 it would focus in anti-frig damage, in L3 in anti-cruiser damage. That's why caracal is very good at L2s, 5x 'Arbalest' assault launcher and 2x T2 Ballistic Control Units kills frigs really fast.